Many homogeneous catalysts are based on organometallic complexes, in particular complexes comprising transition metals. Organometallic complexes comprising η-cyclopentadienyl ligands are particularly useful. This class of electron-rich aromatic ligand is often strongly bound to the metal catalyst, resulting in stable complexes with significant steric bulk around the metal centre. The pentamethylcyclopentadienyl (Cp*) ligand is commonly used in conjunction with transition metal catalysts such as Ru, Rh, Ir, Ti and Fe. Although many benefits may be derived from such catalysts, the catalysts are expensive and therefore may need to be recovered at the end of a reaction to enable economic use. Homogeneous catalysts are, however, often difficult to separate from the product in a simple and economical fashion. To address these limitations, attempts have been made to prepare cyclopentadienyl ligands which are bound to a solid support. However, many of these processes require a complex multi-step synthesis to produce the desired ligands.
WO 2007/096592 discloses a microencapsulated catalyst-ligand system comprising a polymeric ligand encapsulated within a permeable polymer shell. This publication discloses inter alia the encapsulation of cyclopentadienyl ligands, including 1-(3-hydroxypropyl)-2,3,4,5-tetramethylcyclopentadiene, 1-(4-hydroxybutyl)-2,3,4,5-tetra methylcyclopentadiene, 1-(5-hydroxypentyl)-2,3,4,5-tetramethylcyclo pentadiene, 1-(3-aminopropyl)-2,3,4,5-tetramethylcyclopentadiene, 1-(4-aminobutyl)-2,3,4,5-tetramethyl cyclopentadiene, 1-(5-aminopentyl)-2,3,4,5-tetramethylcyclopentadiene and 1-(8-hepta decenyl)-2,3,4,5-tetramethylcyclopentadiene.